1. Field of the Invention
The invention relates to cellular radio communication systems and, more particularly, to the assignment of radio communication channels in such systems.
2. History of the Prior Art
When cellular radio systems were first implemented, specific frequencies within a basic frequency range were as signed for communication between fixed radio base stations and mobile subscribers using analog modulation techniques. Correspondingly, the mobile radio transceivers available to mobile subscribers at that time were capable of transmitting and receiving radio signals only on the assigned radio frequencies within the basic frequency range and could communicate only with analog modulation techniques.
As the use of cellular radio systems increased over the years, the limited number of basic frequencies assigned by the communications authorities for cellular usage became increasingly congested this led to the frequent occurrence of call blockages due to the unavailability of a communication channel frequency for use by a calling or called subscriber. To decrease the level of congestion in cellular radio systems, an additional frequency range, referred to as the extended frequencies, was assigned for use by cellular radio systems. This addition made available an increased number of communication channels in each system, the added frequency channels all lying in the extended frequency band, to accommodate a greater amount of traffic and an increased number of subscribers. However, new mobile transceivers needed to be designed and manufactured which would communicate not only on radio channels within the "basic frequency" range, but also on radio channels within the "extended frequency" range. At this time all communications in both frequency ranges took place using analog modulation. However, since there would then be mobile transceivers operating within the system which were capable of operating in both the basic and extended frequency ranges, as well as mobile transceivers which could only operate within the basic frequency range, it became necessary to have each mobile station identify to the system its frequency capabilities upon seeking access to a communication channel so that a channel assignment could then be made in accordance with the specific frequency capabilities of the requesting mobile transceiver.
When digital modulation techniques began to be used on the radio communication channels available between a base station and a mobile, newer subscriber units were provided with transceivers of the so-called "dual mode" type. Such mobile transceivers are capable of operating with both analog modulation techniques as well as digital modulation techniques within both the basic and extended frequency ranges. This additional capability added another parameter which must be indicated to the system by the mobile when seeking access to a communication channel and which must be evaluated by the system when assigning a communication channel to a mobile seeking access.
In conventional cellular radio telecommunication systems, the decision-making algorithms necessary for the system to assign available communication channels to a mobile as a function of its frequency/modulation capabilities were hard coded into the software of the cellular switch. While these techniques adequately solved the problem at issue by ensuring that each mobile station is only assigned a communication channel according to its particular frequencys and modulation capabilities, they did not allow flexibility in communication channel assignments to be incorporated into the system through taking into consideration parameters other than frequency and modulation. For example, there was no way to allocate communication channels as a function of the priority of service accorded to a particular mobile subscriber or to assign a particular communication channel depending upon the service features to be provided to the subscriber during the connection.
It would be a distinct advantage to enable an operator of a cellular radio system to custom configure the parameters to be employed by the system in allocating communication channel assignments in order to optimize the service provided to a subscriber within the system. It would also be desirable to provide unique call handling priorities within the system as a function of the classes of service subscribed to by individual subscribers.